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/*
* Copyright (c) 2015, Charlie Curtsinger and Emery Berger,
* University of Massachusetts Amherst
* This file is part of the Coz project. See LICENSE.md file at the top-level
* directory of this distribution and at http://github.com/plasma-umass/coz.
*/
#include "inspect.h"
#include <elf.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <cstdint>
#include <iostream>
#include <fstream>
#include <map>
#include <set>
#include <sstream>
#include <string>
#include <system_error>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <libelfin/dwarf/dwarf++.hh>
#include <libelfin/elf/elf++.hh>
#include "util.h"
#include "ccutil/log.h"
using namespace std;
/**
* Locate the build ID encoded in an ELF file and return it as a formatted string
*/
static string find_build_id(elf::elf& f) {
for(auto& section : f.sections()) {
if(section.get_hdr().type == elf::sht::note) {
uintptr_t base = reinterpret_cast<uintptr_t>(section.data());
size_t offset = 0;
while(offset < section.size()) {
Elf64_Nhdr* hdr = reinterpret_cast<Elf64_Nhdr*>(base + offset);
if(hdr->n_type == NT_GNU_BUILD_ID) {
// Found the build-id note
stringstream ss;
uintptr_t desc_base = base + offset + sizeof(Elf64_Nhdr) + hdr->n_namesz;
uint8_t* build_id = reinterpret_cast<uint8_t*>(desc_base);
for(size_t i = 0; i < hdr->n_descsz; i++) {
ss.flags(ios::hex);
ss.width(2);
ss.fill('0');
ss << static_cast<size_t>(build_id[i]);
}
return ss.str();
} else {
// Advance to the next note header
offset += sizeof(Elf64_Nhdr) + hdr->n_namesz + hdr->n_descsz;
}
}
}
}
return "";
}
static string absolute_path(const string filename) {
if(filename[0] == '/') return filename;
char* cwd = getcwd(NULL, 0);
REQUIRE(cwd != NULL) << "Failed to get current directory";
return string(cwd) + '/' + filename;
}
static string canonicalize_path(const string filename) {
vector<string> parts = split(absolute_path(filename), '/');
// Iterate over the path parts to produce a reduced list of path sections
vector<string> reduced;
for(string part : parts) {
if(part == "..") {
REQUIRE(reduced.size() > 0) << "Invalid absolute path";
reduced.pop_back();
} else if(part.length() > 0 && part != ".") {
// Skip single-dot or empty entries
reduced.push_back(part);
}
}
// Join path sections into a single string
string result;
for(string part : reduced) {
result += "/" + part;
}
return result;
}
static bool file_exists(const string& filename) {
struct stat statbuf;
int rc = stat(filename.c_str(), &statbuf);
// If the stat call succeeds, the file must exist
return rc == 0;
}
/**
* Get the full path to a file specified via absolute path, relative path, or raw name
* resolved via the PATH variable.
*/
static const string get_full_path(const string filename) {
if(filename.find('/') != string::npos) {
return canonicalize_path(filename);
} else {
// Search the environment's path for the first match
const string path_env = getenv("PATH");
vector<string> search_dirs = split(getenv_safe("PATH", ":"));
for(const string& dir : search_dirs) {
string full_path = dir + '/' + filename;
if(file_exists(full_path)) {
return full_path;
}
}
}
return "";
}
/**
* Locate an ELF file that contains debug symbols for the file provided by name.
* This will work for files specified by relative path, absolute path, or raw name
* resolved via the PATH variable.
*/
static elf::elf locate_debug_executable(const string filename) {
elf::elf f;
const string full_path = get_full_path(filename);
// If a full path wasn't found, return the invalid ELF file
if(full_path.length() == 0) {
return f;
}
int fd = open(full_path.c_str(), O_RDONLY);
// If the file couldn't be opened, return the invalid ELF file
if(fd < 0) {
return f;
}
// Load the opened ELF file
f = elf::elf(elf::create_mmap_loader(fd));
// If this file has a .debug_info section, return it
if(f.get_section(".debug_info").valid()) {
return f;
}
// If there isn't a .debug_info section, check for the .gnu_debuglink section
auto& link_section = f.get_section(".gnu_debuglink");
// Store the full path to the executable and its directory name
string directory = full_path.substr(0, full_path.find_last_of('/'));
// Build a set of paths to search for a debug version of the file
vector<string> search_paths;
// Check for a build-id section
string build_id = find_build_id(f);
if(build_id.length() > 0) {
string prefix = build_id.substr(0, 2);
string suffix = build_id.substr(2);
auto p = string("/usr/lib/debug/.build-id/") + prefix + "/" + suffix + ".debug";
search_paths.push_back(p);
}
// Check for a debug_link section
if(link_section.valid()) {
string link_name = reinterpret_cast<const char*>(link_section.data());
search_paths.push_back(directory + "/" + link_name);
search_paths.push_back(directory + "/.debug/" + link_name);
search_paths.push_back("/usr/lib/debug" + directory + "/" + link_name);
}
// Clear the loaded file so if we have to return it, it won't be valid()
f = elf::elf();
// Try all the usable search paths
for(const string& path : search_paths) {
fd = open(path.c_str(), O_RDONLY);
if(fd >= 0) {
f = elf::elf(elf::create_mmap_loader(fd));
if(f.get_section(".debug_info").valid()) {
break;
}
f = elf::elf();
}
}
return f;
}
unordered_map<string, uintptr_t> get_loaded_files() {
unordered_map<string, uintptr_t> result;
ifstream maps("/proc/self/maps");
while(maps.good() && !maps.eof()) {
uintptr_t base, limit;
char perms[5];
size_t offset;
size_t dev_major, dev_minor;
uintptr_t inode;
string path;
// Skip over whitespace
maps >> skipws;
// Read in "<base>-<limit> <perms> <offset> <dev_major>:<dev_minor> <inode>"
maps >> std::hex >> base;
if(maps.get() != '-') break;
maps >> std::hex >> limit;
if(maps.get() != ' ') break;
maps.get(perms, 5);
maps >> std::hex >> offset;
maps >> std::hex >> dev_major;
if(maps.get() != ':') break;
maps >> std::hex >> dev_minor;
maps >> std::dec >> inode;
// Skip over spaces and tabs
while(maps.peek() == ' ' || maps.peek() == '\t') { maps.ignore(1); }
// Read out the mapped file's path
getline(maps, path);
// If this is an executable mapping of an absolute path, include it
if(perms[2] == 'x' && path[0] == '/') {
result[path] = base - offset;
}
}
return result;
}
bool wildcard_match(string::const_iterator subject,
string::const_iterator subject_end,
string::const_iterator pattern,
string::const_iterator pattern_end) {
if((pattern == pattern_end) != (subject == subject_end)) {
// If one but not both of the iterators have finished, match failed
return false;
} else if(pattern == pattern_end && subject == subject_end) {
// If both iterators have finished, match succeeded
return true;
} else if(*pattern == '%') {
// Try possible matches of the wildcard, starting with the longest possible match
for(auto match_end = subject_end; match_end >= subject; match_end--) {
if(wildcard_match(match_end, subject_end, pattern+1, pattern_end)) {
return true;
}
}
// No matches found. Abort
return false;
} else {
// Walk through non-wildcard characters to match
while(subject != subject_end && pattern != pattern_end && *pattern != '%') {
// If the characters do not match, abort. Otherwise keep going.
if(*pattern != *subject) {
return false;
} else {
pattern++;
subject++;
}
}
// Recursive call to handle wildcard or termination cases
return wildcard_match(subject, subject_end, pattern, pattern_end);
}
}
bool wildcard_match(const string& subject, const string& pattern) {
return wildcard_match(subject.begin(), subject.end(), pattern.begin(), pattern.end());
}
bool in_scope(const string& name, const unordered_set<string>& scope) {
string normalized = canonicalize_path(name);
for(const string& pattern : scope) {
if(wildcard_match(normalized, pattern)) {
return true;
}
}
return false;
}
void memory_map::build(const unordered_set<string>& binary_scope,
const unordered_set<string>& source_scope) {
//REQUIRE(wildcard_match("/abc/def/ghij", "/abc/def/ghij")) << "ohshit";
for(const auto& f : get_loaded_files()) {
if(in_scope(f.first, binary_scope)) {
try {
if(process_file(f.first, f.second, source_scope)) {
INFO << "Including lines from executable " << f.first;
} else {
INFO << "Unable to locate debug information for " << f.first;
}
} catch(const system_error& e) {
WARNING << "Processing file \"" << f.first << "\" failed: " << e.what();
}
} else {
INFO << f.first << " is not in scope";
}
}
}
dwarf::value find_attribute(const dwarf::die& d, dwarf::DW_AT attr) {
if(!d.valid())
return dwarf::value();
try {
if(d.has(attr))
return d[attr];
if(d.has(dwarf::DW_AT::abstract_origin)) {
const dwarf::die child = d.resolve(dwarf::DW_AT::abstract_origin).as_reference();
dwarf::value v = find_attribute(child, attr);
if(v.valid())
return v;
}
if(d.has(dwarf::DW_AT::specification)) {
const dwarf::die child = d.resolve(dwarf::DW_AT::specification).as_reference();
dwarf::value v = find_attribute(child, attr);
if(v.valid())
return v;
}
} catch(dwarf::format_error e) {
WARNING << "Ignoring DWARF format error " << e.what();
}
return dwarf::value();
}
void memory_map::add_range(std::string filename, size_t line_no, interval range) {
shared_ptr<file> f = get_file(filename);
shared_ptr<line> l = f->get_line(line_no);
// Add the entry
_ranges.emplace(range, l);
}
void memory_map::process_inlines(const dwarf::die& d,
const dwarf::line_table& table,
const unordered_set<string>& source_scope,
uintptr_t load_address) {
if(!d.valid())
return;
try {
if(d.tag == dwarf::DW_TAG::inlined_subroutine) {
string name;
dwarf::value name_val = find_attribute(d, dwarf::DW_AT::name);
if(name_val.valid()) {
name = name_val.as_string();
}
string decl_file;
if(d.has(dwarf::DW_AT::decl_file) && table.valid()) {
decl_file = table.get_file(d[dwarf::DW_AT::decl_file].as_uconstant())->path;
}
size_t decl_line = 0;
dwarf::value decl_line_val = find_attribute(d, dwarf::DW_AT::decl_line);
if(decl_line_val.valid())
decl_line = decl_line_val.as_uconstant();
string call_file;
if(d.has(dwarf::DW_AT::call_file) && table.valid()) {
call_file = table.get_file(d[dwarf::DW_AT::call_file].as_uconstant())->path;
}
size_t call_line = 0;
if(d.has(dwarf::DW_AT::call_line)) {
call_line = d[dwarf::DW_AT::call_line].as_uconstant();
}
// If the call location is in scope but the function is not, add an entry
if(decl_file.size() > 0 && call_file.size() > 0) {
if(!in_scope(decl_file, source_scope) && in_scope(call_file, source_scope)) {
// Does this inline have separate ranges?
dwarf::value ranges_val = find_attribute(d, dwarf::DW_AT::ranges);
if(ranges_val.valid()) {
// Add each range
for(auto r : ranges_val.as_rangelist()) {
add_range(call_file,
call_line,
interval(r.low, r.high) + load_address);
}
} else {
// Must just be one range. Add it
dwarf::value low_pc_val = find_attribute(d, dwarf::DW_AT::low_pc);
dwarf::value high_pc_val = find_attribute(d, dwarf::DW_AT::high_pc);
if(low_pc_val.valid() && high_pc_val.valid()) {
uint64_t low_pc;
uint64_t high_pc;
if(low_pc_val.get_type() == dwarf::value::type::address)
low_pc = low_pc_val.as_address();
else if(low_pc_val.get_type() == dwarf::value::type::uconstant)
low_pc = low_pc_val.as_uconstant();
else if(low_pc_val.get_type() == dwarf::value::type::sconstant)
low_pc = low_pc_val.as_sconstant();
if(high_pc_val.get_type() == dwarf::value::type::address)
high_pc = high_pc_val.as_address();
else if(high_pc_val.get_type() == dwarf::value::type::uconstant)
high_pc = high_pc_val.as_uconstant();
else if(high_pc_val.get_type() == dwarf::value::type::sconstant)
high_pc = high_pc_val.as_sconstant();
add_range(call_file,
call_line,
interval(low_pc, high_pc) + load_address);
}
}
}
}
}
} catch(dwarf::format_error e) {
WARNING << "Ignoring DWARF format error " << e.what();
}
for(const auto& child : d) {
process_inlines(child, table, source_scope, load_address);
}
}
bool memory_map::process_file(const string& name, uintptr_t load_address,
const unordered_set<string>& source_scope) {
elf::elf f = locate_debug_executable(name);
// If a debug version of the file could not be located, return false
if(!f.valid()) {
return false;
}
switch(f.get_hdr().type) {
case elf::et::exec:
// Loaded at base zero
load_address = 0;
break;
case elf::et::dyn:
// Load address should stay as-is
break;
default:
WARNING << "Unsupported ELF file type...";
}
// Read the DWARF information from the chosen file
dwarf::dwarf d(dwarf::elf::create_loader(f));
// Walk through the compilation units (source files) in the executable
for(auto unit : d.compilation_units()) {
try {
string prev_filename;
size_t prev_line;
uintptr_t prev_address = 0;
set<string> included_files;
// Walk through the line instructions in the DWARF line table
for(auto& line_info : unit.get_line_table()) {
// Insert an entry if this isn't the first line command in the sequence
if(in_scope(prev_filename, source_scope)) {
if(prev_address != 0) {
included_files.insert(prev_filename);
add_range(prev_filename,
prev_line,
interval(prev_address, line_info.address) + load_address);
}
}
if(line_info.end_sequence) {
prev_address = 0;
} else {
prev_filename = canonicalize_path(line_info.file->path);
prev_line = line_info.line;
prev_address = line_info.address;
}
}
process_inlines(unit.root(), unit.get_line_table(), source_scope, load_address);
for(const string& filename : included_files) {
INFO << "Included source file " << filename;
}
} catch(dwarf::format_error e) {
WARNING << "Ignoring DWARF format error when reading line table: " << e.what();
}
}
return true;
}
shared_ptr<line> memory_map::find_line(const string& name) {
string::size_type colon_pos = name.find_first_of(':');
if(colon_pos == string::npos) {
WARNING << "Could not identify file name in input " << name;
return shared_ptr<line>();
}
string filename = name.substr(0, colon_pos);
string line_no_str = name.substr(colon_pos + 1);
size_t line_no;
stringstream(line_no_str) >> line_no;
for(const auto& f : files()) {
string::size_type last_pos = f.first.rfind(filename);
if(last_pos != string::npos && last_pos + filename.size() == f.first.size()) {
if(f.second->has_line(line_no)) {
return f.second->get_line(line_no);
}
}
}
return shared_ptr<line>();
}
shared_ptr<line> memory_map::find_line(uintptr_t addr) {
auto iter = _ranges.find(addr);
if(iter != _ranges.end()) {
return iter->second;
} else {
return shared_ptr<line>();
}
}
memory_map& memory_map::get_instance() {
static char buf[sizeof(memory_map)];
static memory_map* the_instance = new(buf) memory_map();
return *the_instance;
}
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